On May 19th, I attended the mission's Operation Readiness Test (ORT) for Deep Impact in the Mission Control room at Jet
Propulsion Laboratory and it's just that - a test of all the operations that will be in play on the night of our encounter with Comet
Tempel 1. I've heard the team refer to it as a "dress rehearsal" and because I have a theater background, I was immediately
interested. If taking two spacecraft to space and using one to take data while another makes a deep crater in a comet is the
assignment, then that's the mission which must be exactly rehearsed. This encounter rehearsal sets the stage in the control room for
our ORT.

Here's what takes place during an ORT. It is like a dress rehearsal in that all the project members are in the seats they will fill
during the encounter, rehearsing all of the operations and sequences of events that will take place on that night. To simulate the
event further, sequences and operations are run at the same hour of day that they will take place during encounter, which for us puts
impact rehearsal at 10:54PM Pacific time. The Deep Impact mission is a bit different from some other space missions in that we have
two teams operating parallel to one another. There is a team for the flyby spacecraft that releases the impactor and then watches the
collision, taking numerous pictures. There is also a team that controls the impactor projectile that is released 24 hours before
encounter and makes the crater that we expect to be 2 - 14 stories deep.

During the rehearsal, commands travel back and forth among the team members and to the test bed in one of the nearby
buildings, which simulates the operations of the spacecraft. There must even be a person in the loop who can serve to rehearse the
operations and commands for the Deep Space Network antennas that will give overlapping coverage to our mission during the
encounter.

Because we will offer coverage to NASA TV on the night of encounter, there also must be a rehearsal on the part of those who
do our media coverage and work with team members who translate the commands to our TV audience. When the ORT reaches the
moment at which the impact has taken place, members of the team who take care of the impactor spacecraft begin to analyze what
they have seen that evening.

But for the flyby spacecraft team, there is still a major job to fulfill as Tempel 1 comes barreling through space in the
direction of the remaining craft. Having only 800 seconds to peer into the inside of the new crater made by its counterpart, the flyby
spacecraft needs careful guidance to tilt slowly up so that its instruments can keep the comet in view. At the same time, members of
the team urgently monitor the precious images the flyby spacecraft has already taken and started to return to Earth as quickly as
possible. At a certain point, part of the team rehearses a halt of the angle at which the craft had tilted to image the inside of the crater.
They will keep the spacecraft at that angle until it has cleared the dust and rock in the tail of Tempel 1. Then they will watch
carefully as the flyby executes commands they wrote long ago to turn and view the departing comet. Their job doesn't ease at all until
as many images as possible can be downloaded to Earth through the DSN antennas which were chosen for their exact location to track
the spacecraft.

As busy as an ORT may seem, remember that on the night of encounter, these things will also be happening at the same time
and some of them without rehearsal.

The science team, some of whom originally dreamt the concept for this mission, will be crowded together in a conference room
around computers looking at the images that have been streaming down to them for the past several hours - trying as quickly as
possible to prepare them to be released to the public and the press. These will be the closest images ever taken of the nucleus of a
comet. For many of these men and women who have fallen in love with these icy travelers, it captures the moment of a lifetime. At
Cornell University in Ithaca, NY, trained members will monitor their computers as they process the data received from the Deep Space
Network and send it to the science team for analysis. As they finish, data is fed back to Jet Propulsion Laboratory and at the same
time to the University of Maryland where the Principal Investigator for the mission makes his home. As images are released with
accompanying information, at least two web masters will be up late directing them to several web sites for the public to view.

Hubble, Spitzer and Chandra-all earth-orbiting telescopes-will also time and position themselves to take images of the impact
and send them directly to ground stations so they can continue eventually on to the science team. Further into space, the Rosetta
mission on its way to its own comet rendezvous will take images to add to the data from space.

One Deep Impact science team member will be missing from the conference room. On the big island of Hawaii and close to the
Mauna Kea telescopes, Karen Meech will be receiving word and images from major ground based telescopes all over the world. One of
her jobs is to put them in order and send them along to her counterparts for comparison to the offerings of the flyby and impactor
spacecraft.

Watching from deserts, mountain tops and open dark plains will be thousands of amateur astronomers, many of whom joined
the Small Telescope Science Program to track Comet Tempel 1 five and a half years ago. These astronomers will submit their
own images along with the science team's as part of the data gathering effort for Deep Impact. Multiple organizations around the
world have set their own programs and plans to image Comet Tempel 1 before the night of encounter and then again, during
and after the impact. Their objective is to look for an increase in the brightness of the coma.

At the moment of impact, equally important and virtually "unrehearsable" things will also be happening. Over 500 master
teachers and ambassadors, who volunteered their time, drove to remote locations, spent nights in strange cities, and stood on their
feet for many hours to bring the Deep Impact mission to the public and schools, will stay up late watching TV's, web sites or traveling
to Hawaii where the impact is easiest to see. For them, it's the moment they have been telling people about for 5years. Two year's
worth of students at Meadow Creek School in Minnesota, who gathered enough pennies to match the mass of copper in the impactor
and then gave the money to their sister school in the Ukraine will sit with their families and watch that projectile reach its destination.
Girl Scout leaders who went through several workshops so that they could encourage young women to become scientists and
engineers will sit at campfires and telescopes telling them that it is really happening up there on that very night. Children who learned
about comets for the first time through a comet song will get to see what they really look like and high schoolers who used Deep
Impact classroom activities to study the same challenges the project team faced and then made their own decisions will see who was
right. Over 625,000 people who entered their names to go on a CD on the side of the impactor will watch as their names make a
Deep Impact!

Scientists, engineers, teachers, speakers, leaders, families and children - a community beginning in 2000 and growing toward encounter
in 2005 to see what is really deep inside a comet will be with us. Some of it can be rehearsed like the ORT - and some of it can't.

'Tell you what though; a NASA mission ORT makes my memories of dress rehearsal as a snowflake in the Magic Nutcracker look
real easy!

Note: The Deep Impact mission is a partnership among the University of Maryland, the Jet Propulsion Laboratory and Ball
Aerospace & Technologies Corp. where the spacecraft and instruments were built.